Gas turbine engines typically comprise an oil tank which holds oil to be used for various purposes, such as for lubrication of various components. During engine operation, temperatures and pressures in the oil tank may rise. A breather line may bleed off excess air pressure in the oil tank. However, the breather line may at times become inefficient. The oil tank may include a fill tube. A cap may be attached to a fill port of the fill tube. A flapper valve may seal a bottom end of the fill tube. The flapper valve may seal the fill tube closed due to a pressure differential between the oil tank and the ambient pressure. When the flapper valve is sealed closed, oil poured down the fill tube may not enter the oil tank through the flapper valve. In the past, mechanics have inserted an object, such as a screwdriver, through the fill tube to force the flapper valve open to release pressure in the oil tank. However, the rapid release of pressure may cause scalding oil to spray out the fill tube.